Air-free lubricant pump discharge system



Dec. 11, 1951 1. R.\WHITEMAN AIR-F REE LUBRICANT PUMP DISCHARGE SYSTEMFiled Sept. 50, 1949 lNVENTOR Irvin R. Whitemun msiti RM ATTORN EYWITNESSES: A v w N L Patented Dec. 11, 1951 AIR-FREE LUBRICANT PUMPDISCHARGE SYSTEM Irvin R. Whiteman, Philadelphia, Pa., assignor, bymesne assignments, to the United States of America as represented by theSecretary of the Navy Application September 30, 1949, Serial No. 118,839

3 Claims.

This invention relates to pressure lubrication systems, and moreparticularly to pressure lubrication apparatus for an aviation gasturbine power plant.

In a pressure lubrication system for a gas turbine engine carried on anaircraft, an oil pump of the rotary type, such as a gear pump, isusually employed for delivering oil under pressure from a reservoir tothe lubrication system. In some designs of turbojet power plants, oilunder pressure from the lubrication system may also be utilized ineffecting hydraulic adjustment of engine auxiliaries, such as a movableexhaust nozzle element. To avoid any tendency towarrd erraticperformance, it is desirable that such a lubrication or hydraulic systembe so devised as to prevent introduction therein of air along with theoil supplied under pressure by the pump, regardless of the position towhich the aircraft and engine might be tilted during flight.

A principal object of the invention is the provision of improved meansfor supplying oil under pressure to a system which will be maintainedsubstantially free of air pockets irrespective of variations in thepositioning of the apparatus.

Another object of the invention is to provide an hydraulic pumpdischarging through a check valve and having a restricted by-passassociated therewith for bleeding off any air inadvertently admitted tothe inlet and discharged by the pump, due to tilting of the apparatus orother cause.

These and other objects are effected by the invention as will beapparent from-the following description and claims taken in connectionwith the accompanying drawing, forming a part of this application, inwhich the single figure is a diagrammatic elevational view of anaviation gas turbine power plant equipped with pressure lubricationmeans constructed in accordance with the invention.

As shown in the drawing, the power plant therein illustrated inschematic form comprises a substantially tubular outer casing structureU having mounted along the axis thereof a sectional inner core structureI2, which with the outer casing defines an annular flow passageway l3that extends longitudinally through the plant from a forwardly-directedair intake opening I 4 to a rearwardly-disposcd jet nozzle lb. Thecasing structure I I is adapted to be mounted in or on the fuselage orwing of a suitable aircraft (not shown) with the intake opening itpointed in the direction of flight. Mounted within the power plant inaxial alignment and defining the core structure 12 are an axial-flowcompressor l1, combustion apparatus I8, and a turbine 20, which isoperatively connected to the compressor through the medium of a shaft2|. The turbo-compressor rotor aggregate thus comprising the turbine 20,the compressor I1 and shaft 2| is rotatably mounted in three bearings22, 23 and 24 suitably supported within the core structure l2.

In accordance with the well-known principle of operation of a gasturbine engine, air entering the intake opening it is compressed by thecompressor ii and delivered through the passageway l3 to the combustionapparatus l8, where fuel, supplied by means of a suitable manifold andnozzles (not shown), is burned to provide motive fluid for driving theturbine 20. Motive fluid exhausted from the turbine 20 is thandischarged by way of the nozzle I5 in the form of a jet establishing apropulsive thrust.

For eiiecting lubrication of operating parts ofthe engine including thebearings 22, 23 and 24, there may be provided a lubrication systemwhich, as shown in an elementary form, comprises a reservoir 26, anengine driven oil pump 21, a cooler 28, and a scavenging pump 29. Itwill be understood that in actual practice, a

complete lubrication system might include ad ditional well knownelements and control devices, which have here been omitted. Such asystem might also be arranged to furnish motive power for auxiliaries,such as a suitable type of movable nozzle assembly (not shown). For thepurposes of disclosure of the present invention, however, the system maybe considered as effecting distribution of oil to the engine bearings,by operation of the pump 21 to draw oil from the reservoir 26 by way ofan inlet communication 30 and to discharge oil under pressure through apipe 3| and through the cooler 28 to a manifold pipe 32 leading tobearings 22, 23 and 24. The scavenging pump 29 is at the same timeoperative with the oil pump 21 to draw excess oil from the bearings, byway of a scavenge pipe 25, the scavenged oil being returned through adischarge pipe 25a to the reservoir 26.

According to the invention, a check valve device 33 is interposed in thepipe 3| at the discharge side of the pump 21. The'check valve device 33comprises a casing having a chamber 34 containing a valve element 35,which is urged toward its seat by a coil spring, 36 and'jis adapted tobe unseated by pressure of; cit-i oimally discharged from the pump byway of a discharge communication am. A by-pass 3'! having a choke orrestricted orifice 38 of predetermined flow area is provided formaintaining a controlled bleed communication between the pump dischargecommunication am, at a point upstream with relation to the check valvedevice 33, and a scavenge zone such as the scavenge pipe 25.

In operation, with the apparatus in a normal or substantially horizontalposition, as shown in the drawing, the oil pump inlet communication 36is submerged under the level of. Oil contained in the reservoir 2G, sothat oil can be pumped therefrom through the check valve device 33 tothe lubrication system in the usual manner. The restricted orifice-3.8,while permitting flow at a slow rate of oil of normal viscosity throughthe by-pass 3'. to the scavenged communication 25, is so proportionedrelative to the oil output capacity of the pump 2i as to rendernegligible the effect of such a restricted bleed. of oil upon operation01 the system as a whole.

On the other hand, the orifice 38 is large enough to pass a volume ofair at a relatively rapid rate. Thus, if for any reason the apparatus istilted to bring the level of oil to t. e position indicated at A, sothat the inlet communication 39 of the pump 2? is uncovered, causingadmission of air to the pump, substantially all of the air discharged bythe pump will then be diverted back from the discharge communication Bidthrough the by-pass 3? to the scavenge communication 25, since with theby-pass always open, the oil pump cannot build up air pressuresufiicient to effect unseating of the check valve 35.

From the foregoing it will be seen that the improvement arrangement ofelements of the pressure lubricationv system can readily be incorporatedin aviation power plant equipment of current or advanced design Without.necessitating. extensive modifications, and will efifectively pram ventaccess of air to the lubrication system during operation in an inclinedposition, while ensuring rapid repriming of the purnp upon resumption ofthe normal or horizontal position of the apparatus.

While the invention has been shown in but one form, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various other changes and modifications without departingfrom the spirit thereof.

What is claimed is:

1. Means for preventing access of air tov an oil pressure systemincluding an oil pump for supplying oil thereto through a dischargecommunication and a scavenge pump for withdrawing excess oil from saidsystem through a scavenge communication, said means comprising aspringpressed check valve interposed in said discharge communication fornormally passing oil under pressure delivered by said oil pump, and arestricted. by-pass communicating withv said discharge communication at.a. point anterior to said check valve and with said scavenge communication on the inlet side of said scavenge pump, said by-pass having apredetermined flow area substantially retarding flow of fluid having theviscosity of oil normally delivered by said oil pump, While venting airinadvertently discharged by said pump to prevent build-up of airpressure suihcient to open said check valve.

2. In an aviation power plant having a pressure lubrication systemjoined to a supply reservoir, an oil pump, the inlet of which isnormally submerged in oil in the reservoir, for supplying oil to thesystem through a discharge communication, a scavenge pumpfor withdrawingoil from the system through a scavenge communication, said scavenge pumpbeing in communication with the reservoir, means comprising a springpressed check valve interposed in discharge communication for normallypassing oil under pressure delivered by said oil pump, and a restrictedby-pass communicating with said discharge com munication at a pointanterior to said check valve and with said scavenge communication on thein let side of said scavenge pump, said by-pass having a predeterminedflow area substantially retarding flow of fluid having the viscosity ofoil normally delivered by said oil pump, While bleeding airinadvertently discharged by said pump, said scavenge pump returning theoil and air from the re stricted by-pass back to the supply reservoir..

3. The combination of claim. 2 further defined in that the restrictedby-pass is formed by a relatively largev passage for the major portionof its length and said large passage has a short. restricted portionjoining two of said large portions.

IBVIN R. WHITEMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,456,886 Mori Dec. 21, 19482,503,016 Weeks Apr. 4, 1950 FOREIGN PATENTS Number Country Date 128,170Austria May 10, 1932 880,952 France Jan. 11, 1943

